Papers

Runaway stars ejected from the Galactic disc span a range of velocities, with two extreme regimes of particular interest. Hyper-runaway stars reach velocities approaching the local Galactic escape speed while remaining gravitationally bound to the Galaxy, while hypervelocity stars (HVS) have speeds which exceed the escape speed, leaving them formally unbound. Studying both populations places stringent constraints on star cluster formation, supernova explosions in massive binaries, and the shape of the stellar halo. Here we present a spectroscopic search for such extreme-velocity stars using data from the first data release of the Dark Energy Spectroscopic Instrument (DESI DR1). Because these objects are typically located at distances beyond the range where gaia parallaxes are reliable, we derive stellar parameters through a combined analysis of spectroscopy and spectral energy distributions (SEDs). These parameters are then compared with stellar evolutionary tracks to infer distances, which are subsequently used to compute the kinematics of the candidates. We identify a sub-sample of eight stars that appear unbound to the Galaxy, likely of extragalactic origin. These stars exhibit projected rotational velocities exceeding $50$ km s$^{-1}$, consistent with a main-sequence nature. An additional eleven stars are identified as potential HVS candidates under the assumption that they are main-sequence stars. This interpretation is not supported by their rotational velocities, making their unbound status less secure. Finally, $26$ stars show evidence of being main-sequence runaway stars ejected from the Galactic disc. The fastest object in the sample is a metal-poor HVS candidate with a Galactocentric velocity upper-limit of $934 \pm 110$ km s$^{-1}$. The star with the largest measured radial velocity of $513$ km s$^{-1}$ is most likely a slowly pulsating B-type runaway star.

The chemical potentials of charged multi-component mixtures are central to electrolyte thermodynamics, but remain difficult to compute from atomistic simulations. The S0 method enables computing chemical potentials of mixtures from equilibrium molecular dynamics simulations. Here we extend the S0 method to charged mixtures by combining the composition-space framework developed in Part I: Neutral Multi-component Mixtures with a Coulombic treatment of the small-wavenumber limits of static structure factors. This approach separates thermodynamically relevant neutral composition fluctuations from forbidden macroscopic charge fluctuations, and further accounts for charge-neutrality constraints. We use the method to compute the chemical potentials of multiple-halide aqueous salt solutions, elucidating the ion-specific thermodynamic effects. We also calculate the mixing free energies of molten salt mixtures, demonstrating the importance of correctly describing long-wavelength electrostatic correlations.

We systematically investigate the zoom-whirl periodic orbits of a small compact object orbiting a magnetically charged black hole in $f(R, T)$ gravity coupled with Euler-Heisenberg nonlinear electrodynamics. We evaluate the impact of the magnetic charge $Q_m$ and the Euler-Heisenberg parameter $a$ on the characteristics of the innermost stable circular orbit (ISCO) and the marginally bound orbit (MBO). Particularly, we focus on the precession parameter q and systematically examine how the magnetic charge and other parameters affect the trajectories of periodic orbits. Using the numerical kludge method, we generate gravitational waveforms for these periodic orbits. The results presented in our work demonstrate that the magnetic charge can significantly modify not only the precession parameter but also the orbital trajectories of the periodic orbits. Moreover, changing the magnetic charge $Q_m$ could cause a significant phase shift in the gravitational waveforms, while other parameters exert a relatively weaker influence on the gravitational waves.

Black Holes are the key to solving many unanswered questions in fundamental physics: in particular, the very extreme properties shown by supermassive black holes at the centers of galaxies make them obvious candidates for testing gravity theories in the strong-field regime. Since X-rays are generated by matter under extreme physical conditions, ultra-high resolution X-ray imaging (uXRI) will directly image the region near the event horizon of black holes in X-rays, similar to the Event Horizon Telescope in the radio band, enabling unprecedented tests of General Relativity and alternative theories of gravity near supermassive black holes. On the other hand, clusters of galaxies hold the potential of unveiling many unknowns in cosmology. uXRI will unlock this potential by probing small-scale plasma properties in the intracluster medium, providing the missing link required to establish galaxy clusters as reliable tools for high-precision cosmology. Moreover, uXRI will enable mapping of Dark Matter from galaxy cluster dynamics via proper motion measurements. Finally, uXRI will open a new field of precision X-ray astrometry, allowing for measuring pulsar parallaxes to support nanoHertz gravitational wave searches.

We study admissible higher-spin algebras in four-dimensional Minkowski space, namely algebras that admit the tower of massless higher-spin fields as a representation. Under several simplifying assumptions, we show that these can be of two types, which we refer to as collinear and half-collinear. The chiral higher-spin algebra provides an example of the latter. For the collinear ansatz considered here, direct solution of the Jacobi identity yields two families of Lie algebras. We also find an associative collinear algebra, which is commutative unless internal degrees of freedom are added.

We formulate collider observables based on quantum steering ellipsoids (QSEs) for reconstructed bipartite systems of spin-$1/2$ particles. A collider spin density matrix defines a two-qubit state, while its QSE gives the geometry of conditional states accessible through local measurements. This makes the ellipsoid a direct probe of the quantum properties of fundamental particles, encoding polarization, spin correlation anisotropy, accessible-state volume, and the orientation of the dominant correlation axes. Using top-quark pair production as a benchmark process, we show how QSE observables organize the Standard Model spin state, probe entanglement, steerability, and Bell-nonlocality criteria, and use an expected precision metric to assess sensitivity to non-local correlations in the boosted central region. We show that different dimension-six operators generate distinctive QSE deformations, and provide a geometric interpretation of quantum information observables in high-energy particle physics. Quantum steering geometry therefore provides a unified framework for particle collider tomography, quantum information diagnostics, and precision searches for physics beyond the Standard Model with applications spanning the HL–LHC and future lepton, muon, flavor, and electron-ion collider programs.

In recent years, kirigami metamaterials have been widely studied and applied in science and engineering. While various two- and three-dimensional kirigami design methods have been developed, most of them are only applicable to a limited class of kirigami structures. In this work, we develop a unified framework for kirigami design that encompasses a wide range of 2D-to-2D, 2D-to-3D, and 3D-to-3D shape-morphing effects, as well as additional geometric and physical properties such as compact reconfigurability and rigid deployability. In particular, by reformulating the design task as a length-based constrained optimization problem and solving it simultaneously for multiple target states of the kirigami structure, our unified design framework enables greater design flexibility and stronger theoretical support. Experimental results with a wide range of shape-morphing effects are presented to demonstrate the effectiveness of our framework. We further present a rigorous theoretical analysis of several key aspects of kirigami design, covering inertia transposition, aspect-ratio law, and angle defects, thereby elucidating important design rules and limitations. Altogether, our work paves a new way for the design of shape-morphing mechanical metamaterials.

The $\gamma$ Cephei system hosts one of the first exoplanets discovered and is orbited by one of the closest known stellar companions to a planet-hosting star. Here, we derive updated orbital fits for $\gamma$ Cep AB, the stellar binary, and Ab, the planet, by combining literature data with Hipparcos-Gaia astrometry, new radial velocities (RVs), and adaptive optics imaging. We acquired 328 RVs of $\gamma$ Cep A with Keck/HIRES, AFP/Levy, McDonald/Tull, and Whipple/TRES, and eight adaptive optics imaging epochs with Keck/NIRC2, including the earliest spatially resolved image of $\gamma$ Cep B in 2003. These observations extend the precision RV baseline of $\gamma$ Cep to 45 years and the direct imaging baseline to 23 years, improving inferred orbital parameter precisions by a factor of 2–10 compared to previous work. For $\gamma$ Cep B, we derive a semi-major axis of $a_B=20.07 \pm 0.06$ AU, a mass of $M_B=415 \pm 2$ $M_{Jup}$ ($0.396 \pm 0.002$ $M_{\odot}$), an eccentricity of $e_B=0.422 \pm 0.002$, and an inclination of $i_B=119.8^{\circ}\pm0.1^{\circ}$. For $\gamma$ Cep Ab, we find a separation of $a_{Ab}=1.978 \pm 0.007$ AU, a minimum mass of $M_{Ab} \sin i = 1.62 \pm 0.04$ $M_{Jup}$, and an eccentricity of $e_{Ab}=0.07 \pm0.03$. Using the RV residuals and dynamical constraints, we rule out additional Jovians between 2.5–20 AU, and companions more massive than Neptune for $a<1$ AU, both at $>90\%$ confidence. The absence of additional giant planets over a broad range of orbital separations is consistent with a dynamically sculpted system in which the close stellar companion limited the formation or long-term survival of other distant companions.

Vortex pinning is central to the standard interpretation of pulsar glitches, but the mechanical load exerted by a pinned vortex array on the solid crust has received less attention than the angular-momentum reservoir itself. We calculate the axisymmetric elastic response of a continuously stratified neutron-star crust to this load using realistic SLy4 and BSk21 stellar backgrounds and composition-dependent Coulomb shear moduli. The superfluid-crust lag sets the Magnus force, while the mesoscopic pinning force of Seveso et al. (2016) provides a local upper bound. At low lag the response is linear; progressive local saturation then produces a broad transition and a finite high-lag envelope. The stress maximum is robustly located at the deep crustal boundary towards the rotation axis, although the local Magnus force vanishes on-axis, showing that the localization is produced by global elastic-gravitational redistribution. Realistic elasticity changes the stress amplitude by 10-20 per cent relative to the common mu=10^-2 P prescription and reverses the SLy4-BSk21 ordering. At a Vela-motivated lag of 10^-2 rad s^-1, the maximum strain is only 3.1 x 10^-5 (SLy4) and 4.7 x 10^-5 (BSk21), remaining below 1.4 x 10^-4 on the formal plateau. A 1.2-2.0 solar-mass scan changes the stress amplitude by only about 20 per cent and leaves the deep-polar localization unchanged. Pinning therefore supplies a structured and astrophysically relevant crustal pre-stress, but cannot by itself break an initially relaxed crust.

In this work we investigate how exotic spinorial topology modifies the propagation of fermionic modes in the Schwarzschild geometry. By incorporating a topological gradient, $\partial_\mu\varphi$, into the Dirac operator through a tetrad deformation, we show that the exotic spinorial sector naturally induces an effective geometric deformation of the Schwarzschild background. The central consequence of this construction is the emergence of a topological impedance surface at $\rtopo=1/q$, which suppresses the radial group velocity of the exotic spinorial modes, yielding a birefringent propagation pattern. Using a spinorial perturbation we discuss the greybody factor and the quasinormal response. The quasinormal spectrum shows the stability of the background metric and the absence of isospectrality for the superpartner potentials.

We prove, under some assumptions, the uniqueness of universal quantum dimension formulae. We first show that the quantum dimensions of classical algebras have a specific form that can be represented universally, in Vogel's sense, as the product/ratio of q-dimension factors with arguments $a\alpha+b\beta+c\gamma$ where $c=0, 1, 2$ and $a, b$ are integers. On this basis, we derive simple uniqueness criteria, according to which all known universal quantum dimensions are unique.

We explore the prevalence of mini-quenched or “napping” galaxies selected from spectroscopic and photometric samples in the UNCOVER/MegaScience survey. These galaxies are empirically identified by the presence of moderate Balmer breaks, weak emission lines ($EW(H\alpha) < 100$A) and relatively blue UV continua. We infer the star formation histories (SFHs) of our sample using flexible non-parametric models with Prospector optimized to capture recent episodes of bursty star formation and quenching, and find that they are uniquely identifiable in the SFR$_{10}$/SFR$_{100}$ parameter space moving towards (temporary) quiescence. We demonstrate that although spectroscopy is best able to identify rapidly declining SFRs, densely sampled medium-band photometry recover these key spectral features and thus robustly identify pure samples of this transient phase – with imaging alone. We quantify the number density of napping galaxies at $z=4-7$ in the Abell 2744 lensing field, finding 8 spectroscopically confirmed nappers and 60 photometric candidates spanning log$_{10}$(M$_*$/M$_\odot$) $= 7.5-10$. We verify that the photometry alone can identify a pure sample of nappers, leveraging a smaller high signal-to-noise ratio spectroscopic sample. Consistent with previous studies, we find that nappers are most common at low stellar mass (log$_{10}$(M$_*$/M$_\odot$) $\sim9$). We see a hint that the number densities increase from $z\sim6$ to $z\sim4$, though our small sample is likely affected by cosmic variance. Our study demonstrates the increasing importance of stochastic star formation as a regulator of low-mass galaxy growth in the several hundred Myr after reionization, and offers a direct observational testbed for the strength and duty cycle of stellar feedback in cosmological simulations.

The interplay between twist-angle engineering and unconventional magnetism provides a powerful new route to control quantum phenomena. We theoretically investigate a heterostructure comprising a $d$-wave superconductor proximitized by a two-dimensional $d$-wave altermagnet. We reveal that the momentum-space mismatch between the superconducting gap nodes and the altermagnetic spin-splitting nodes generates a robust, twist-tunable odd-frequency spin-triplet pairing. Consequently, the macroscopic electromagnetic response of the system can be tuned from a conventional diamagnetic Meissner state to an anomalous paramagnetic Meissner effect driven entirely by the interfacial twist angle. For a $d_{x^2-y^2}$ altermagnet, the paramagnetic response is maximized at perfect alignment ($\phi=0$) and completely suppressed at a maximal twist of $\phi=\pi/4$, while a $d_{xy}$ altermagnet exhibits the exact complementary behavior. Our results establish twisted altermagnetic heterostructures as a versatile platform for engineering odd-frequency pairing and macroscopic superconducting phases.

Submillimeter observations of polarized dust emission from molecular clouds to starless cores frequently report a decrease in polarization fraction (p) with increasing dust emission intensity (I). This feature is commonly attributed to the alignment loss of dust grains or the geometrical effects of magnetic fields, yet, the detailed contributions remain unclear. To investigate the mechanism responsible for the depolarization, we use POLARIS to perform the multiscale synthetic dust polarization observations at $850\mu m$ from magnetically aligned dust grains by RAdiative Torques (RATs) mechanism. We adopt three collapsing cloud models with different magnetic energy levels and explore the effects of grain magnetic properties and grain growth on dust polarization. The field geometrical effect is the dominant depolarization mechanism at $N_{\rm H}<10^{21}-10^{22}\rm cm^{-2}$. We find that if grains grow beyond $>0.5\mu m$ and are superparamagnetic (SPM) with large iron clusters, RATs remain effective at high column densities, and grain alignment loss contributes to depolarization only at $N_{\rm H} > 10^{23}\rm cm^{-2}$. If neither of these conditions is satisfied, the alignment loss (in cases of insufficient grain growth); or the reduced grain alignment efficiency by gaseous damping (for paramagnetic grains or SPM grains with small iron cluster sizes) can become the dominant depolarization mechanism at $N_{\rm H} > 10^{22}\rm cm^{-2}$, regardless of how tangled the magnetic field lines in our simulation. Finally, we show that the depolarization mechanism and the underlying dust physical properties inside starless cores may be identified through the $p-I$ slope and the mean p at the core center.

Disordered dynamical systems comprising many interacting units, from ecological communities to neural circuits, are ubiquitous, and understanding how connectivity shapes their collective behavior is a central theoretical challenge. One long-recognized feature of neural circuits is local connectivity balance, in which the excitatory and inhibitory weights converging onto each unit approximately cancel. Although local connectivity balance has been proposed to serve functions such as gating incoming signals, its effect on collective network dynamics remains unclear. Here we analytically study randomly connected recurrent networks with varying degrees of local connectivity balance. We show that this balance leaves the connectivity spectrum unchanged yet drastically reshapes the dynamics in a manner that depends critically on the single-unit nonlinearity. Local balance suppresses unbounded growth of the network state and stabilizes network dynamics when the activation function scales linearly or faster, whereas it drives the network into chaos when the activation function is sub-linear or saturating. Importantly, these effects vanish for odd activation functions, which are commonly assumed in previous work. We further find that, for saturating nonlinearities, the effective dimension of the dynamics varies nonmonotonically with the degree of balance. We show that all these phenomena arise from a unifying mechanism: the suppression of a self-generated feedback input by local connectivity balance. Our results identify local connectivity balance as a previously overlooked control parameter for collective dynamics in realistic disordered networks.

Fractal geometries provide a distinctive platform for controlling quantum interference, topology, and localization. We investigate the Su–Schrieffer–Heeger (SSH) model constructed on the Koch curve, where a triangular geometry enables additional same-sublattice hoppings that break chiral symmetry and modify the conventional topological behavior captured by a real-space local marker. Destructive interference within the triangular units produces a highly degenerate flat level at $E=-t$. Although this level originates from the local geometry, its degeneracy and spectral weight are controlled by the self-similar connectivity of the Koch curve. The hierarchy reduces the number of independent flat states and reorganizes the spectrum into an intricate distribution of energy levels. Our results reveal complementary roles for local triangular interference and global fractal connectivity in shaping the electronic properties of geometrically modified SSH chains.

This survey introduces the role of frame phase retrieval in pure-state identification and information preservation by quantum channels. For unit vectors, the lift $x\mapsto xx^*$ identifies vectors that differ only by a global phase with the same rank-one quantum state, converts frame intensities into linear functionals of the lifted state, and makes the adjoint pullback of output observables an operator-valued measurement on the input system. From this viewpoint, a channel is phase retrievable exactly when it is injective on pure states. We develop this correspondence through Choi-rank-two linear combinations of Kraus operators, higher-rank relative spectra, structural obstructions, and constructions with prescribed Choi rank. We distinguish injective identification from full tomography, perfect one-shot discrimination, zero-error classical communication, and exact quantum correction. Twirling channels then provide a structured setting in which commutants, irreducible dimensions, multiplicities, orbit-frame orthogonality, coding indices, and phase-retrievable subspaces can be read from group representations.

The observation that the coherence lengths in cuprate superconductors are extremely small motivated us to search for its real-space structure by examining the consequence of hole-doping in CuO4 units in cuprates. We analyzed aggregates of hole-doped CuO4 units that phase-separate from hole-doped CuO2 layers in terms of their segregation-pressure indices defined in this work. Our search suggests that each d-wave Cooper pair is an antiferromagnetically coupled spin dimer protected in an antiferromagnetic hole dimer (AHD), and that the antiferromagnetic chains of AHDs provide channels through which such spin dimers can move collectively without perturbation. Based on these suggestions and their implications, we examined the causes for several seemingly puzzling observations on cuprate superconductors to find that they are naturally explained by the suggestions.

We report the structural and vibrational properties of the prototypical 4$f$-filled nonmagnetic member LuN of the lanthanide nitrides, LnN, with elastic and inelastic neutron scattering data at $4$~K. We find a peak in the generalized density of states which, through input from a DFT+$U$ computation, we ascribe to a van Hove singularity on the fourfold-degenerate $L$-face of the Brillouin zone. This work advances the understanding of phonon dynamics in LnN beyond the $\Gamma$-point.

We investigate directed transport in a one-dimensional Brownian flashing ratchet with a piecewise-linear asymmetric periodic potential. Numerical solutions of the Fokker–Planck equation and Brownian dynamics simulations reveal a nonmonotonic dependence of the stationary current on the switching frequency, with a resonant maximum whose position depends on the potential asymmetry $\delta$ and barrier height $\Delta$. For moderate asymmetry, $|\delta|<0.5$, the current obeys a scaling form that separates the dependence on the potential parameters from a common frequency dependence, resulting in a data collapse upon appropriate scaling of the current and frequency. The current amplitude varies linearly with $\delta$, while the resonance frequency follows $\nu(\delta,\Delta)=\nu_0(\Delta)/ [1-b_0\, \delta^2]$. We interpret the resulting $(1-\delta^2)^{-1}$ scaling in terms of coupled relaxation along the two branches of the asymmetric potential, which provides a physical basis for the observed dependence of the resonant frequency on the potential asymmetry.

This paper establishes an operator-theoretic version of Pego's compactness theorem within the framework of quantum harmonic analysis on general locally compact abelian phase spaces. We show that a bounded set of Hilbert-Schmidt operators is precompact if and only if it is uniformly equicontinuous under phase-space shifts and its Fourier-Weyl transform is uniformly equicontinuous on the dual phase space. We provide applications to quantum physics.

For a free scalar particle in one spatial dimension, in a single-pass half-line geometry, we compare the absorbing Robin boundary condition with the generalized Marchewka–Schuss (MS) unidirectional-current family. Robin absorption is characterized by a single parameter $\kappa>0$: once $\kappa$ is specified, its momentum-dependent absorption profile is fixed. In the generalized MS construction, by contrast, the detector response is described by a spectral function $\lambda(k)$, subject to the positivity and subnormalization conditions of the detection law. We show that every Robin choice of $\kappa$ corresponds to the particular MS calibration $\lambda_\kappa(k)=\pi\kappa/(k+\kappa)^2$, which reproduces the complete Robin absorption current for every admissible one-sided spectral amplitude and at every time. Thus the entire one-parameter Robin absorption family is contained within the generalized MS family. The MS construction is more general: the choice $\lambda_{\rm full}(k)=\pi/(4k)$ gives unit absorption efficiency for every wave number, which cannot be achieved by any fixed Robin parameter. In this precise sense, the generalized MS detector process extends the Robin absorbing-boundary family. We also compare their asymptotic behavior in the ballistic fixed-ray regime and in the fixed-distance late-time limit.

We present a novel approach to computing the Nijenhuis torsion and Frölicher-Nijenhuis brackets of recursion operators for symmetries, based on their full-fledged forms introduced by Jahnová and Vojčák (2024). In contrast to the conventional approach, which represents recursion operators as maps between shadows of nonlocal symmetries within a given covering, our method allows the Nijenhuis torsion to be computed directly from its defining formula, without requiring any additional mathematical constructions. The same framework can also be used to compute the Frölicher-Nijenhuis bracket of recursion operators and to verify their compatibility directly in their full-fledged forms. The procedure is illustrated by several examples of full-fledged recursion operators for symmetries of differential equations in four independent variables, including a new recursion operator for the four-dimensional universal hierarchy equation that, to the best of our knowledge, has not previously appeared in the literature. A notable feature of this new full-fledged recursion operator is that its shadow component does not appear to admit a reasonable representation in any of the standard conventional forms. Nevertheless, our approach allows us to prove directly that the Nijenhuis torsion of this operator vanishes. For the examples considered, the corresponding Frölicher-Nijenhuis brackets also vanish, confirming the compatibility of the respective pairs of recursion operators. This demonstrates that full-fledged forms provide an effective framework for studying the hereditary and compatibility properties of recursion operators, including highly nonlocal and/or multidimensional cases that are difficult to handle by existing methods.

We report the first numerical examination of symmetric mass generation (SMG) for domain-wall fermions. Our simulation on a two-dimensional Euclidean lattice computes the path-integral of the Fidkowski-Kitaev Majorana chain with two boundaries, corresponding to the two (physical and mirror) walls. We demonstrate by evaluating the lattice Dirac operator eigenvalue spectrum that the local four-Fermi interaction selectively gaps the edge fermions on the mirror wall while leaving the physical wall intact. We further identify a characteristic signature of SMG in the path-integral: the gap of the Dirac operator opens along the imaginary axis of the complex spectrum, in contrast to the standard mass shift in the real direction. The conventional hybrid Monte Carlo algorithm remains practical with reweighting the complex phase of the Pfaffian, which is found to be remarkably small throughout the simulation. These results provide a practical nonperturbative framework for interaction-induced mirror-fermion decoupling of lattice domain-wall fermions.

Any type of attractor basin (classic-graph) created in DDLab can now be visualised, manipulated, and deconstructed as a drag/drop “interactive state transition graph” (istr-graph). The new istr-graph applies to subtrees, single basins, the basin of attraction field, compression, and all other classic-graph parameters. This is an important update on the pre-existing “interactive basin of attraction field graph” (ibaf-graph) specific to just the complete uncompressed field, but the ibaf-graph is nevertheless retained for some of its unique attributes. These issues are discussed with a focus on the scope and implementation of the new istr-graph.

We prove that the stationary density fluctuation field of the one-dimensional weakly asymmetric simple inclusion process converges to the energy solution of the stochastic Burgers equation. The key technical ingredient is a second-order Boltzmann-Gibbs principle tailored to the microscopic current. As a consequence, we also obtain Ornstein-Uhlenbeck fluctuations for the symmetric inclusion process in a weakly condensing regime, a result of independent interest.

We investigate the quantum statistical effects of bosonic warm dark matter (BWDM) in a microscopic model in which dark radiation (DR) is produced through the annihilation process $\chi\chi\rightarrow\phi\phi$ mediated by a Yukawa interaction. By decomposing the BWDM phase-space distribution into thermal and Bose–Einstein condensed components, we derive the thermally averaged annihilation cross sections for the thermal–thermal, thermal–condensate, and condensate–condensate channels, including the Sommerfeld enhancement. We find that, for the relatively small scalar DR masses considered here, the thermal–condensate channel remains subdominant. The transition between the thermal–thermal dominated and condensate–condensate dominated regimes is characterized by a critical condensate fraction $r_{\rm c}$, which depends mainly on the BWDM mass and the scalar DR mass. For condensate fractions above this critical value, the condensate–condensate channel can dominate the present-day annihilation rate. We further constrain the BWDM parameter space using the observational upper bound on the additional effective number of relativistic species, $\Delta N_{\mathrm{eff}}$.

This study presents a theoretical investigation of generalized solute dispersion in magnetohydrodynamic multiphase tube flow with porous layers. A two-fluid analytical model is developed for applications in biofluid and environmental fluid dynamics. The model comprises a micropolar (non-Newtonian) fluid core representing the rotational behaviour of red blood cells and a Newtonian plasma periphery embedded with Brinkman and Darcy porous structures, corresponding to the glycocalyx and endothelial layers with distinct permeability characteristics. A transverse magnetic field is incorporated to investigate how magnetic-field-induced modifications of the carrier flow influence solute localisation, with potential relevance to magnetic nanoparticle-mediated drug delivery. Using the generalised dispersion framework of Sankarasubramanian & Gill, analytical solutions are derived to investigate how the coupled axial velocity field and associated microrotational dynamics influence solute transport. The analytical predictions are independently validated through Brownian dynamics simulations, demonstrating excellent agreement for the temporal evolution of the zeroth and first transport moments. The results reveal the previously unexplored influence of microrotational dynamics on solute concentration, convection coefficients and effective dispersion, providing new insights into the coupled roles of translational and rotational fluid motion in biofluid transport. This work bridges an important gap in the literature and establishes a generalized theoretical framework linking magnetic fields, micropolar fluids and porous arterial structures for biofluid transport, targeted drug delivery and clinical engineering applications.

Streaming-potential-mediated transport of viscoelastic fluids has attracted research attention owing to its applications in electrokinetic energy conversion and microfluidic transport. Existing analytical and semi-analytical models in published literature provide valuable physical insights, but require repeated numerical evaluations for exploring large design spaces and identifying the optimal operating conditions. In this work, a surrogate-assisted framework is developed for rapid design optimization of pressure-driven electrokinetic transport of simplified Phan-Thien-Tanner fluids in a slit microchannel. A high-fidelity numerical database is generated over a broad range of governing dimensionless parameters, which includes the zeta potential, the Debye parameter, the Dukhin number, and the viscoelastic parameter. A Machine Learning surrogate model is subsequently trained to accurately approximate the nonlinear relationship between the governing parameters and the streaming potential, while the volumetric flow rate and hydroelectric energy conversion efficiency were calculated from closed form equation by using the streaming potential predicted by the surrogate. This is coupled with a multi-objective optimization strategy to identify operating conditions that simultaneously maximize energy conversion efficiency and volumetric flow rate. The proposed methodology can significantly accelerate parametric exploration compared with repeated numerical simulations across different parameters and provides practical design guidelines for electrokinetic microfluidic devices. The study demonstrates the potential of combining computational fluid mechanics with data-driven surrogate modeling for efficient engineering design and optimization.

We determine the exact entanglement structure of the conditional state obtained by measuring $m$ corresponding rungs ($m\leq N/2$) in two identical copies of an arbitrary half-filled free fermion Gaussian state and post-selecting the same normalized single-fermion state ($|\psi\rangle = u|10\rangle+v|01\rangle$, where 0 and 1 denote the fermion occupancy on each sites) on each rung. For $m<N/2$, the conditional wavefunction generally depends on the initial state. Nevertheless, whenever the selected outcome has nonzero probability, the state on the unmeasured sites remains Gaussian and factorizes exactly into $N-m$ different orthogonal modes including $m$ inter-copy entangling modes and $N-2m$ spectator modes localized in one copy. Consequently, the entanglement entropy between the unmeasured parts of the two copies is $S=m h_2(|v|^2)$, independent of the initial state, where $h_2(x)=-x\ln x-(1-x)\ln(1-x)$. The success probability is given by $P_m=\det C_L\det(I_m-C_L)=\det(C_{LR}C_{RL})$, determined solely by the initial correlations and independent of ($u$,$v$). Equal-weight Bell post-selection serves as a special case that achieves the maximal entanglement swapping.